【单选题】Why is Tambora mentioned in this clip?
A.
To remember the people wh died in that event.
B.
To show how powerful volcanoes are.
C.
To warn people to stay away from Tambora.
D.
To show how weak people were at that time.
【单选题】实体完整性要求主属性不能取空值,这一点可以通过( )来保证。
【单选题】关系数据模型中用来保证实体完整性的是______。
【单选题】实体完整性要求主属性不能取空值,这通常是通过( )。
【单选题】实体完整性要求主属性不能为空值,这一点可以通过( )来保证。
【单选题】实体完整性规则要求主属性不能取空值,为此,可通过______来保证。
【简答题】词形变化。 1. Why not go _________(boat) on the river with me? 2. The children like _______( swim) in the lake. 3. Do you enjoy _______(teach) English in our class, Mr. Green? 4. Are you ______(go)______(h...
【单选题】实体完整性要求主属性不能取空值,这一点通常是通过( )。